Related Experiment Video

Updated: Jul 11, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
06:22

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice

Published on: September 17, 2015

Determinants of frequency-dependent contraction and relaxation of mammalian myocardium

Paul M L Janssen1, Muthu Periasamy

  • 1Department of Physiology and Cell Biology, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210-1218, USA. janssen.10@osu.edu

Journal of Molecular and Cellular Cardiology
|October 9, 2007
PubMed

Insights

Heart rate increases boost cardiac output through more beats and stronger contractions. This review explores how heart cells adapt to faster rates, ensuring efficient heart function during exercise and stress.

Area of Science:

  • Cardiology
  • Physiology

Background:

  • Cardiac output regulation is vital for meeting metabolic demands during exercise and stress.
  • Increased heart rate is a primary driver of elevated cardiac output.
  • Myocardial force generation and relaxation kinetics are critical for maintaining cardiac function at higher rates.

Purpose of the Study:

  • To review the cellular mechanisms underlying frequency-dependent cardiac activation.
  • To elucidate how intracellular calcium handling and myofilament responsiveness change with heart rate.
  • To understand the basis of faster cardiac activation and relaxation kinetics.

Main Methods:

  • Literature review focusing on cellular and molecular mechanisms.
  • Analysis of studies investigating calcium transients in cardiomyocytes.
  • Examination of research on myofilament properties and their rate-dependence.

Main Results:

  • Higher heart rates lead to faster cardiac activation and relaxation.
  • Intracellular calcium transient dynamics are modulated to accommodate increased frequency.
  • Myofilament responsiveness to calcium is altered, contributing to rate-dependent force changes.

Conclusions:

  • Cellular adaptations in calcium handling and myofilament function are essential for maintaining cardiac output at elevated heart rates.
  • Understanding these mechanisms is key to comprehending heart performance during physiological stress.
  • Rate-dependent changes in cardiac kinetics are crucial for adequate ventricular filling and function.

More Related Videos

Mechanical Control of Relaxation Using Intact Cardiac Trabeculae07:51

Mechanical Control of Relaxation Using Intact Cardiac Trabeculae

Published on: February 17, 2023

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling08:29

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling

Published on: August 1, 2016

Related Concept Videos

Specialized Characteristics of Cardiac Muscles01:27

Specialized Characteristics of Cardiac Muscles

The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...
Pathophysiology of Cardiac Performance01:29

Pathophysiology of Cardiac Performance

Typical heart performance is influenced by heart rate, rhythm, myocardial contraction, and metabolism or blood flow. The cardiac muscle exhibits distinct electrophysiological features, including pacemaker activity and calcium channel control, which play a vital role in the heart's response to various drugs. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate. Sympathetic activation increases heart rate, while parasympathetic activation...
Muscle Stimulation Frequency01:22

Muscle Stimulation Frequency

The contraction strength of muscles is regulated by motor neurons, which modulate the frequency of action potentials dispatched to the motor units based on the body's requirements. This process of varying the muscle stimulation frequency allows muscles to contract with a force that is precisely tailored to the needs of the moment, whether lifting a feather or a heavy box.
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
Smooth Muscle Contraction01:25

Smooth Muscle Contraction

Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Motor Unit Stimulation01:20

Motor Unit Stimulation

When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...